WO2021006284A1

WO2021006284A1 - Polyimide resin, polyimide varnish, and polyimide film

Info

Publication number: WO2021006284A1
Application number: PCT/JP2020/026619
Authority: WO
Inventors: 舜星野; 三田寺　淳
Original assignee: 三菱瓦斯化学株式会社
Priority date: 2019-07-10
Filing date: 2020-07-08
Publication date: 2021-01-14
Also published as: JPWO2021006284A1; CN114096589B; CN114096589A; KR20220034059A; TW202106765A

Abstract

This polyimide resin has structural unit A derived from a tetracarboxylic acid di-anhydride and structural unit B derived from a diamine, wherein the structural unit A includes structural unit (A-1) derived from a compound represented by formula (a-1) but does not include structural unit (A-2) derived from a compound represented by formula (a-2), the structural unit B includes structural unit (B-1) derived from a compound represented by formula (b-1) and structural unit (B-2) derived from a compound represented by formula (b-2), the proportion of structural unit (B-1) in structural unit B is 30-70 mol%, and the proportion of structural unit (B-2) in structural unit B is 70-30 mol%.

Description

Polyimide resin, polyimide varnish and polyimide film

The present invention relates to a polyimide resin, a polyimide varnish and a polyimide film.

Various uses of polyimide resins are being studied in fields such as electrical and electronic components. For example, it is desired to replace a glass substrate used in an image display device such as a liquid crystal display or an OLED display with a plastic substrate for the purpose of reducing the weight and flexibility of the device, and a polyimide film suitable as the plastic substrate. Research is underway.
In an image display device, when light emitted from a display element is emitted through a plastic substrate, colorless transparency is required for the plastic substrate, and light passes through a retardation film or a polarizing plate ( For example, a liquid crystal display, a touch panel, etc.) are required to have high optical isotropic properties (that is, low Rth) in addition to colorless transparency.

Various polyimide resins are being developed in order to satisfy the above-mentioned required performance. For example, Patent Document 1 states that 3,3'-diaminodiphenylsulfone (first diamine), 4,4′-diaminodiphenylsulfone and the like are used as polyimide resins that provide a polyimide film that is colorless and transparent, has a low Rth, and has excellent toughness. A polyimide resin produced by using a combination with a specific diamine (second diamine) as a diamine component is described.
Further, in Patent Document 2, the applicant states that as a polyimide resin having a high refractive index, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride and 3,3', 4,4'-biphenyl are used as dicarboxylic acid components. A polyimide using a combination of tetracarboxylic acid dianhydride and a combination of 4,4'-diaminodiphenyl sulfone and bis [4- (4-aminophenoxy) phenyl] phenyl as a diamine is disclosed.

International Publication No. 2016/158825 International Publication No. 2017/195574

By the way, in order for a polyimide film to be suitable as a substrate, not only colorless transparency and optical isotropic properties, but also chemical resistance (for example, acid resistance and alkali resistance) are important physical properties.
For example, when a polyimide film is used as a substrate for forming an ITO (Indium Tin Oxide) film, the polyimide film is required to have resistance to the acid used for etching the ITO film. If the acid resistance of the polyimide film is insufficient, the film may turn yellow and the colorless transparency may be impaired.
Further, an alkaline aqueous solution such as a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution is mainly used for cleaning a support (a support to which a polyimide varnish is applied) such as a glass plate used in manufacturing a polyimide film. .. Cleaning with an alkaline aqueous solution may be performed even when a polyimide film is formed on a support such as a glass plate. Therefore, the polyimide film is also required to have resistance to alkali.
However, in Patent Document 1, the chemical resistance is not evaluated.

When the polyimide film is used as a substrate, a target electronic circuit is formed on the polyimide film through various steps such as a sputtering step and an etching step for forming a metal film depending on the application. If the film is not in close contact with a support such as a glass plate, a problem will occur in the process. In addition, a step of peeling the polyimide film from the support is required after these processes. At that time, the polyimide film is required to have a certain toughness, that is, high strength and good elongation in order to facilitate the process and prevent breakage during peeling.
Furthermore, when producing polyimide, various monomers are combined, but depending on the type of monomer, the reactivity is poor, and if an attempt is made to increase the molecular weight of the polyimide, polymerization takes an excessive amount of time. Therefore, polymerization is performed from the viewpoint of production cost. There was a need to save time.

The present invention has been made in view of such a situation, and the subject of the present invention is a film having excellent colorless transparency, optical isotropic property, chemical resistance (for example, acid resistance and alkali resistance), and toughness. It is an object of the present invention to provide a polyimide resin which can be formed and has a short polymerization time, and a polyimide varnish and a polyimide film containing the polyimide resin.

The present inventors have found that a polyimide resin containing a combination of specific structural units can solve the above-mentioned problems, and have completed the invention.

That is, the present invention relates to the following [1] to [3].
[1] A polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine.
The structural unit A includes a structural unit (A-1) derived from a compound represented by the following formula (a-1), and a structural unit (A) derived from a compound represented by the following formula (a-2). -2) is not included,
A structural unit (B-1) in which the structural unit B is derived from a compound represented by the following formula (b-1) and a structural unit (B-2) derived from a compound represented by the following formula (b-2). Including and
A polyimide resin in which the ratio of the structural unit (B-1) in the structural unit B is 30 to 70 mol%, and the ratio of the structural unit (B-2) in the structural unit B is 70 to 30 mol%.

[2] A polyimide varnish obtained by dissolving the polyimide resin according to the above [1] in an organic solvent.
[3] A polyimide film containing the polyimide resin according to the above [1].

According to the present invention, it is possible to form a film having excellent colorless transparency, optical isotropic property, chemical resistance (for example, acid resistance and alkali resistance), and toughness, and the polymerization time of the polyimide resin is short.

[Polyimide resin]
The polyimide resin of the present invention has a structural unit A derived from tetracarboxylic acid dianhydride and a structural unit B derived from diamine, and the structural unit A is derived from a compound represented by the following formula (a-1). The structural unit (A-1) is included, and the structural unit (A-2) derived from the compound represented by the following formula (a-2) is not included, and the structural unit B is the following formula (b-1). It contains a structural unit (B-1) derived from the compound represented by the compound and a structural unit (B-2) derived from the compound represented by the following formula (b-2). The ratio of the structural unit (B-1) in the structural unit B is 30 to 70 mol%, and the ratio of the structural unit (B-2) in the structural unit B is 70 to 30 mol%.

<Structural unit A>
The structural unit A is a structural unit derived from the tetracarboxylic dianhydride occupying the polyimide resin, and includes the structural unit (A-1) derived from the compound represented by the following formula (a-1), and , Does not include the structural unit (A-2) derived from the compound represented by the following formula (a-2).

The compound represented by the formula (a-1) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride.
When the structural unit A includes the structural unit (A-1), the colorless transparency, optical isotropic property, and chemical resistance of the film can be improved.
The compound represented by the formula (a-2) is a 4,4'-oxydiphthalic anhydride. Since the structural unit A does not include the structural unit (A-2), the polymerization time of the polyimide resin can be shortened.

The ratio of the constituent unit (A-1) in the constituent unit A is preferably 90 mol% or more, more preferably more than 95 mol%, still more preferably 97 mol% or more, and particularly preferably 100 mol%. That is, it is particularly preferable that the structural unit A is composed of only the structural unit (A-1).

The structural unit A may include a structural unit other than the structural unit (A-1). The tetracarboxylic dianhydride giving such a constituent unit is not particularly limited, but is pyromellitic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 9,9'. Arophilic tetracarboxylic dianhydrides such as -bis (3,4-dicarboxyphenyl) fluorene dianhydride and 4,4'-(hexafluoroisopropyridene) diphthalic acid dianhydride (provided that the formula (a-2) is used. ); 1,2,3,4-cyclobutanetetracarboxylic dianhydride and norbornane-2-spirio-α-cyclopentanone-α'-spirio-2''-norbornan-5 , 5'', 6,6''-Alicyclic tetracarboxylic dianhydride such as tetracarboxylic dianhydride (excluding the compound represented by the formula (a-1)); and 1,2, , 3,4-Butanetetracarboxylic dianhydride and other aliphatic tetracarboxylic dianhydrides.
In the present specification, the aromatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more aromatic rings, and the alicyclic tetracarboxylic dianhydride has one alicyclic ring. It means a tetracarboxylic dianhydride containing the above and does not contain an aromatic ring, and the aliphatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing neither an aromatic ring nor an alicyclic ring.
The structural unit arbitrarily included in the structural unit A may be one type or two or more types.

<Structural unit B>
The structural unit B is a structural unit derived from diamine in the polyimide resin, and is a structural unit (B-1) derived from a compound represented by the following formula (b-1) and the following formula (b-2). Includes a structural unit (B-2) derived from the compound represented by.

The compound represented by the formula (b-1) is 3,3'-diaminodiphenyl sulfone.
When the structural unit B includes the structural unit (B-1), the optical isotropic property and chemical resistance of the film can be improved.
The compound represented by the formula (b-2) is a bis [4- (4-aminophenoxy) phenyl] sulfone.
When the structural unit B includes the structural unit (B-2), the toughness of the film is excellent, that is, the tensile elongation can be improved.

The ratio of the structural unit (B-1) in the structural unit B is 30 to 70 mol%, preferably 40 to 65 mol%, and more preferably 50 to 60 mol%. When the ratio of the structural unit (B-1) in the structural unit B is within the range, the polymerization time of the polyimide resin is relatively short, which is preferable.
The ratio of the structural unit (B-2) in the structural unit B is 70 to 30 mol%, preferably 60 to 35 mol%, and more preferably 50 to 40 mol%. When the ratio of the structural unit (B-2) in the structural unit B is within the range, the polymerization time of the polyimide resin is relatively short, which is preferable.
The molar ratio [(B-1) / (B-2)] of the structural unit (B-1) and the structural unit (B-2) in the structural unit B is preferably 30/70 to 70/30. , More preferably 40/60 to 65/35, and even more preferably 50/50 to 60/40.
When the ratio or molar ratio of the structural unit (B-1) and the structural unit (B-2) is within the above range, the polymerization time can be shortened, and the transparency and toughness (elastic modulus) of the obtained polyimide resin can be shortened. , Strength and elongation) can be improved.

In particular, from the viewpoint of polymerization time, the molar ratio [(B-1) / (B-2)] of the structural unit (B-1) and the structural unit (B-2) in the structural unit B is preferably 50. It is / 50 to 70/30, more preferably 55/45 to 70/30, and even more preferably 60/40 to 70/30.
Further, especially from the viewpoint of toughness (strength and elongation) and transparency, the molar ratio of the structural unit (B-1) to the structural unit (B-2) in the structural unit B [(B-1) / ( B-2)] is preferably 30/70 to 60/40, more preferably 30/70 to 55/45, and even more preferably 30/70 to 50/50.

The total ratio of the structural units (B-1) and (B-2) in the structural unit B is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more. It is particularly preferably 99 mol% or more. The upper limit of the total ratio of the structural units (B-1) and (B-2) is not particularly limited, that is, 100 mol%. The structural unit B may consist only of the structural unit (B-1) and the structural unit (B-2).

The structural unit B may include a structural unit other than the structural units (B-1) and (B-2). The diamine that provides such a constituent unit is not particularly limited, but is limited to 1,4-phenylenediamine, p-xylylene diamine, 3,5-diaminobenzoic acid, 1,5-diaminonaphthalene, and 2,2'-dimethyl. Biphenyl-4,4'-diamine, 2,2'-bis (trifluoromethyl) benzidine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 2,2-bis (4-aminophenyl) hexa Fluoropropane, 4,4'-diaminodiphenylsulfone, 4,4'-diaminobenzanilide, 1- (4-aminophenyl) -2,3-dihydro-1,3,3-trimethyl-1H-inden-5- Amin, α, α'-bis (4-aminophenyl) -1,4-diisopropylbenzene, N, N'-bis (4-aminophenyl) terephthalamide, 4,4'-bis (4-aminophenoxy) biphenyl , 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 9,9-bis (4-aminophenyl) Aromatic diamines such as fluorene and 4,4'-diamino-2,2'-bistrifluoromethyldiphenyl ether (excluding compounds represented by formula (b-1)); 1,3-bis (aminomethyl). ) Alicyclic diamines such as cyclohexane and 1,4-bis (aminomethyl) cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine.
In the present specification, the aromatic diamine means a diamine containing one or more aromatic rings, and the alicyclic diamine means a diamine containing one or more alicyclic rings and not containing an aromatic ring, and is a fat. The group diamine means a diamine that does not contain an aromatic ring or an alicyclic ring.
The structural unit arbitrarily included in the structural unit B may be one type or two or more types.

Examples of the diamine that gives the structural unit arbitrarily included in the structural unit B include a compound represented by the following formula (b-3-1), a compound represented by the following formula (b-3-2), and the following formula (b). The compound represented by -3-3) and the compound represented by the following formula (b-3-4) are preferable. That is, in the polyimide resin of one aspect of the present invention, the structural unit B is a structural unit (B-3-1) derived from a compound represented by the following formula (b-3-1), and the following formula (b-3). The structural unit (B-3-2) derived from the compound represented by -2), the structural unit (B-3-3) derived from the compound represented by the following formula (b-3-3), and the following. It may further contain at least one structural unit (B-3) selected from the group consisting of structural units (B-3-4) derived from the compound represented by the formula (b-3-4).

(In formula (b-3-2), R is independently a hydrogen atom, a fluorine atom or a methyl group.)

The compound represented by the formula (b-3-1) is 4,4'-diamino-2,2'-bistrifluoromethyldiphenyl ether.
By including the structural unit (B-3-1) in the structural unit B, the colorless transparency of the film can be improved.

In the formula (b-3-2), R is independently a hydrogen atom, a fluorine atom, or a methyl group, and is preferably a hydrogen atom. The compounds represented by the formula (b-3-2) include 9,9-bis (4-aminophenyl) fluorene, 9,9-bis (3-fluoro-4-aminophenyl) fluorene, and 9,9. Examples thereof include -bis (3-methyl-4-aminophenyl) fluorene, and 9,9-bis (4-aminophenyl) fluorene is preferable.
When the structural unit B includes the structural unit (B-3-2), the optical isotropic property and heat resistance of the film can be improved.

The compound represented by the formula (b-3-3) is 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane.
When the structural unit B includes the structural unit (B-3-3), the colorless transparency of the film can be improved.

The compound represented by the formula (b-3-4) is 2,2'-bis (trifluoromethyl) benzidine.
When the structural unit B includes the structural unit (B-3-4), the colorless transparency, chemical resistance, and mechanical properties of the film can be improved.

When the constituent unit B includes the constituent unit (B-1), the constituent unit (B-2), and the constituent unit (B-3), the constituent unit (B-1) and the constituent unit (B-) in the constituent unit B. The total ratio of 2) is preferably 70 to 95 mol%, more preferably 75 to 95 mol%, still more preferably 75 to 90 mol%, and the constituent unit (B-3) in the constituent unit B. ) Is preferably 5 to 30 mol%, more preferably 5 to 25 mol%, and even more preferably 10 to 25 mol%.
The total ratio of the structural unit (B-1), the structural unit (B-2), and the structural unit (B-3) in the structural unit B is preferably 75 mol% or more, more preferably 80 mol%. The above is more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the ratio of the total of the structural unit (B-1), the structural unit (B-2), and the structural unit (B-3) is not particularly limited, that is, 100 mol%. The structural unit B may be composed of only the structural unit (B-1), the structural unit (B-2), and the structural unit (B-3).

The structural unit (B-3) may be only the structural unit (B-3-1), may be only the structural unit (B-3-2), or may be only the structural unit (B-3-3). It may be only, or it may be only a structural unit (B-3-4).
Further, the structural unit (B-3) may be a combination of two or more structural units selected from the group consisting of the structural units (B-3-1) to (B-3-4).

The number average molecular weight of the polyimide resin of the present invention is preferably 5,000 to 200,000 from the viewpoint of the mechanical strength of the obtained polyimide film. The number average molecular weight of the polyimide resin can be obtained from, for example, a standard polymethylmethacrylate (PMMA) conversion value measured by gel filtration chromatography.

The polyimide resin of the present invention may contain a structure other than the polyimide chain (a structure in which the structural unit A and the structural unit B are imide-bonded). Examples of the structure other than the polyimide chain that can be contained in the polyimide resin include a structure containing an amide bond.
The polyimide resin of the present invention preferably contains a polyimide chain (a structure in which a structural unit A and a structural unit B are imide-bonded) as a main structure. Therefore, the ratio of the polyimide chain to the polyimide resin of the present invention is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and particularly preferably 99% by mass. % Or more.

By using the polyimide resin of the present invention, it is possible to form a film having excellent colorless transparency, optical isotropic property, chemical resistance (for example, acid resistance and alkali resistance), and toughness, which is suitable for the film. The physical property values are as follows.
The total light transmittance is preferably 88% or more, more preferably 88.5% or more, and further preferably 89% or more when the film has a thickness of 10 μm.
The yellow index (YI) is preferably 4.0 or less, more preferably 2.5 or less, and further preferably 2.0 or less when the film has a thickness of 10 μm.
b ^* is preferably 2.0 or less, more preferably 1.2 or less, and further preferably 1.0 or less when the film has a thickness of 10 μm.
The absolute value of the thickness retardation (Rth) is preferably 70 nm or less, more preferably 60 nm or less, and further preferably 35 nm or less when the film has a thickness of 10 μm. Within this range, the optical isotropic property is excellent.
The tensile strength is preferably 105 MPa or more, more preferably 110 MPa or more, and further preferably 115 MPa or more. The tensile elongation is preferably 5 to 20%, more preferably 5 to 15%. When both the tensile strength and the tensile elongation are in this range, the toughness of the film is excellent, the polyimide film can be easily peeled off from the support, and breakage during peeling can be prevented.
The mixed acid ΔYI is preferably 1.5 or less, more preferably 1.3 or less, and further preferably 1.0 or less when the film has a thickness of 10 μm.
The mixed acid Δb ^* is preferably 0.8 or less, more preferably 0.6 or less, and further preferably 0.5 or less when the film has a thickness of 10 μm.
The mixed acid ΔYI and the mixed acid Δb ^* mean the difference in YI and the difference in b ^* before and after the immersion of the polyimide film in the mixture of phosphoric acid, nitric acid and acetic acid, respectively. It can be measured by the method described in the example. The smaller ΔYI and Δb ^* , the better the acid resistance. By using the polyimide resin of the present invention, a film having excellent chemical resistance can be formed, and it also exhibits excellent resistance to acids. In particular, it exhibits excellent resistance to the above acid mixture.

The film that can be formed using the polyimide resin of the present invention has good mechanical properties and heat resistance, and has the following suitable physical property values.
The tensile elastic modulus is preferably 2.0 GPa or more, more preferably 2.5 GPa or more, and further preferably 3.0 GPa or more.
The glass transition temperature (Tg) is preferably 250 ° C. or higher, more preferably 270 ° C. or higher, and even more preferably 300 ° C. or higher. Within this range, the polyimide substrate has heat resistance suitable for manufacturing an image display device such as a liquid crystal display or an OLED display.
The above-mentioned physical property values in the present invention can be specifically measured by the method described in Examples.

[Manufacturing method of polyimide resin]
The polyimide resin of the present invention contains a tetracarboxylic dian component containing a compound giving the above-mentioned structural unit (A-1) (however, does not contain the compound giving the above-mentioned structural unit (A-2)) and the above-mentioned structural unit. It can be produced by reacting a diamine component containing a compound giving (B-1) and a compound giving the above-mentioned structural unit (B-2).

Examples of the compound giving the structural unit (A-1) include the compound represented by the formula (a-1), but the compound is not limited to this, and may be a derivative thereof as long as the same structural unit is given. Examples of the derivative include a tetracarboxylic acid (that is, 1,2,4,5-cyclohexanetetracarboxylic acid) corresponding to the tetracarboxylic dianhydride represented by the formula (a-1) and an alkyl of the tetracarboxylic acid. Esters can be mentioned. As the compound giving the structural unit (A-1), the compound represented by the formula (a-1) (that is, dianhydride) is preferable.

The tetracarboxylic acid component contains the compound giving the structural unit (A-1) in an amount of preferably 90 mol% or more, more preferably more than 95 mol%, still more preferably 97 mol% or more, still more preferably 100. Contains mol%.

The tetracarboxylic acid component may contain a compound other than the compound giving the constituent unit (A-1), and examples of the compound include the above-mentioned aromatic tetracarboxylic dianhydride and alicyclic tetracarboxylic dianhydride. And aliphatic tetracarboxylic dianhydrides, and derivatives thereof (tetracarboxylic dians, alkyl esters of tetracarboxylic dians, etc.).
The compound arbitrarily contained in the tetracarboxylic acid component may be one kind or two or more kinds.

Examples of the compound giving the structural unit (B-1) include the compound represented by the formula (b-1), but the compound is not limited to this, and may be a derivative thereof as long as the same structural unit is given. Examples of the derivative include diisocyanates corresponding to the diamine represented by the formula (b-1). As the compound giving the structural unit (B-1), the compound represented by the formula (b-1) (that is, diamine) is preferable.
Examples of the compound giving the structural unit (B-2) include the compound represented by the formula (b-2), but the compound is not limited to this, and may be a derivative thereof as long as the same structural unit is given. Examples of the derivative include diisocyanates corresponding to the diamine represented by the formula (b-2). As the compound giving the structural unit (B-2), the compound represented by the formula (b-2) (that is, diamine) is preferable.

The diamine component preferably contains a compound that gives the structural unit (B-1) in an amount of 30 to 70 mol%, more preferably 40 to 65 mol%, and even more preferably 50 to 60 mol%. When the ratio of the compound giving the structural unit (B-1) in the diamine component is within the above range, the polymerization time of the polyimide resin is relatively short, which is preferable.
The diamine component preferably contains a compound that gives the structural unit (B-2) in an amount of 70 to 30 mol%, more preferably 60 to 35 mol%, still more preferably 50 to 40 mol%. When the ratio of the compound giving the structural unit (B-2) in the diamine component is within the above range, the polymerization time of the polyimide resin is relatively short, which is preferable.
The molar ratio [(B-1) / (B-2)] of the compound giving the structural unit (B-1) and the compound giving the structural unit (B-2) in the diamine component is preferably from 30/70 to. It is 70/30, more preferably 40/60 to 65/35, and even more preferably 50/50 to 60/40.

In particular, from the viewpoint of polymerization time, the molar ratio of the compound giving the structural unit (B-1) to the compound giving the structural unit (B-2) in the diamine component [(B-1) / (B-2)]. Is preferably 50/50 to 70/30, more preferably 55/45 to 70/30, and even more preferably 60/40 to 70/30.
Further, particularly from the viewpoint of toughness (strength and elongation) and transparency, the molar ratio of the compound giving the structural unit (B-1) and the compound giving the structural unit (B-2) in the diamine component [(B). -1) / (B-2)] is preferably 30/70 to 60/40, more preferably 30/70 to 55/45, and even more preferably 30/70 to 50/50.

The diamine component contains, in total, a compound giving the structural unit (B-1) and a compound giving the structural unit (B-2) in an amount of 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol. % Or more, particularly preferably 99 mol% or more. The upper limit of the total content ratio of the compound giving the structural unit (B-1) and the compound giving the structural unit (B-2) is not particularly limited, that is, 100 mol%. The diamine component may consist only of a compound giving a structural unit (B-1) and a compound giving a structural unit (B-2).

The diamine component may contain a compound other than the compound giving the structural unit (B-1) or (B-2), and the compound includes the above-mentioned aromatic diamine, alicyclic diamine, and aliphatic diamine, and them. Derivatives of (diamine, etc.) can be mentioned.
The compound arbitrarily contained in the diamine component (that is, a compound other than the compound giving the structural unit (B-1) or (B-2)) may be one kind or two or more kinds.

Examples of the compound arbitrarily contained in the diamine component include a compound that gives a structural unit (B-3) (that is, a compound that gives a structural unit (B-3-1), and a compound that gives a structural unit (B-3-2). At least one selected from the group consisting of a compound giving a structural unit (B-3-3) and a compound giving a structural unit (B-3-4)) is preferable.
Examples of the compound giving the structural unit (B-3) include a compound represented by the formula (b-3-1), a compound represented by the formula (b-3-2), and a compound represented by the formula (b-3-3). Examples thereof include the compound represented by the compound and the compound represented by the formula (b-3-4), but the present invention is not limited to this, and a derivative thereof may be used as long as the same structural unit can be formed. Examples of the derivative include diisocyanates corresponding to diamines represented by the formulas (b-3-1) to (b-3-4). As the compound that gives the structural unit (B-3), at least one (that is, diamine) selected from the group consisting of the compounds represented by the formulas (b-3-1) to (b-3-4) is used. preferable.

When the diamine component contains a compound that gives a structural unit (B-1), a compound that gives a structural unit (B-2), and a compound that gives a structural unit (B-3), the diamine component is a structural unit (B-1). ) And the constituent unit (B-2) are preferably contained in an amount of 70 to 95 mol%, more preferably 75 to 95 mol%, still more preferably 75 to 90 mol%, and the constituent unit ( The compound giving B-3) is preferably contained in an amount of 5 to 30 mol%, more preferably 5 to 25 mol%, still more preferably 10 to 25 mol%.
The diamine component contains a compound that gives the structural unit (B-1), a compound that gives the structural unit (B-2), and a compound that gives the structural unit (B-3) in total, preferably 75 mol% or more, and more. It preferably contains 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total content ratio of the compound giving the structural unit (B-1), the compound giving the structural unit (B-2), and the compound giving the structural unit (B-3) is not particularly limited, that is, 100. Mol%. The diamine component may consist only of a compound that gives a structural unit (B-1), a compound that gives a structural unit (B-2), and a compound that gives a structural unit (B-3).

The compound that gives the structural unit (B-3) may be only the compound that gives the structural unit (B-3-1), or may be only the compound that gives the structural unit (B-3-2). It may be only a compound giving a structural unit (B-3-3), or it may be only a compound giving a structural unit (B-3-4).
The compound that gives the structural unit (B-3) is a combination of two or more compounds selected from the group consisting of the compounds that give the structural unit (B-3-1) to (B-3-4). May be good.

In the present invention, the ratio of the amount of the tetracarboxylic acid component to the diamine component charged in the production of the polyimide resin is preferably 0.9 to 1.1 mol of the diamine component with respect to 1 mol of the tetracarboxylic acid component.

Further, in the present invention, in addition to the above-mentioned tetracarboxylic acid component and diamine component, an end-capping agent may be used for producing the polyimide resin. As the terminal encapsulant, monoamines or dicarboxylic acids are preferable. The amount of the end-capping agent to be introduced is preferably 0.0001 to 0.1 mol, particularly preferably 0.001 to 0.06 mol, based on 1 mol of the tetracarboxylic acid component. Examples of the monoamine terminal sealant include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-. Ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline and the like are recommended. Of these, benzylamine and aniline can be preferably used. As the dicarboxylic acid terminal encapsulant, dicarboxylic acids are preferable, and a part thereof may be ring-closed. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenonedicarboxylic acid, 3,4-benzophenonedicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1. , 2-Dicarboxylic acid, etc. are recommended. Of these, phthalic acid and phthalic anhydride can be preferably used.

The method for reacting the above-mentioned tetracarboxylic acid component with the diamine component is not particularly limited, and a known method can be used.
As a specific reaction method, (1) a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, stirred at room temperature to 80 ° C. for 0.5 to 30 hours, and then heated to imidize. Method of carrying out the reaction, (2) After charging the diamine component and the reaction solvent into the reactor and dissolving them, the tetracarboxylic acid component is charged, and if necessary, the mixture is stirred at room temperature to 80 ° C. for 0.5 to 30 hours, and then Examples thereof include a method of carrying out an imidization reaction by raising the temperature to (3) a method of charging a tetracarboxylic acid component, a diamine component and a reaction solvent into a reactor and immediately raising the temperature to carry out the imidization reaction.

The reaction solvent used in the production of the polyimide resin may be one that does not inhibit the imidization reaction and can dissolve the produced polyimide resin. For example, an aprotic solvent, a phenol solvent, an ether solvent, a carbonate solvent and the like can be mentioned.

Specific examples of the aprotonic solvent include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, tetramethylurea and the like. Amide-based solvents, lactone-based solvents such as γ-butyrolactone and γ-valerolactone, phosphorus-containing amide-based solvents such as hexamethylphosphoric amide and hexamethylphosphintriamide, and sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide, and sulfolane. Examples thereof include based solvents, ketone solvents such as acetone, cyclohexanone and methylcyclohexanone, amine solvents such as picolin and pyridine, and ester solvents such as acetic acid (2-methoxy-1-methylethyl).

Specific examples of the phenolic solvent include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4. -Xylenol, 3,5-xylenol and the like can be mentioned.
Specific examples of the ether solvent include 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, 1,2-bis (2-methoxyethoxy) ethane, and bis [2- (2-methoxyethoxy) ethyl]. Examples include ether, tetrahydrofuran, 1,4-dioxane and the like.
Specific examples of the carbonate solvent include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate and the like.
Among the above reaction solvents, an amide solvent or a lactone solvent is preferable. Moreover, the above-mentioned reaction solvent may be used alone or in mixture of 2 or more types.

In the imidization reaction, it is preferable to carry out the reaction while removing water generated during production using a Dean-Stark apparatus or the like. By performing such an operation, the degree of polymerization and the imidization rate can be further increased.

In the above imidization reaction, a known imidization catalyst can be used. Examples of the imidization catalyst include a base catalyst and an acid catalyst.
Base catalysts include pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N, N. Examples thereof include organic base catalysts such as dimethylaniline and N, N-diethylaniline, and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogencarbonate and sodium hydrogencarbonate.
Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, paratoluenesulfonic acid, naphthalenesulfonic acid and the like. Can be mentioned. The above-mentioned imidization catalyst may be used alone or in combination of two or more.
Of the above, from the viewpoint of handleability, it is preferable to use a base catalyst, more preferably an organic base catalyst, further preferably triethylamine, and particularly preferably a combination of triethylamine and triethylenediamine.

The temperature of the imidization reaction is preferably 120 to 250 ° C., more preferably 160 to 200 ° C. from the viewpoint of suppressing the reaction rate and gelation. The reaction time is preferably 0.5 to 6 hours, more preferably 0.5 to 5.5 hours after the start of distillation of the produced water. The reaction time of the polyimide resin of the present invention is relatively short.

The solid content concentration during the imidization reaction is preferably 30 to 60% by mass, more preferably 35 to 58% by mass, and particularly preferably 40 to 56% by mass. When the solid content concentration at the time of the imidization reaction is within this range, the imidization reaction proceeds satisfactorily and the water generated during the reaction can be easily removed, so that the degree of polymerization and the imidization rate can be increased.
However, the solid content concentration at the time of the imidization reaction is a value calculated from the following formula based on the mass of the tetracarboxylic acid component added into the reaction system, the diamine component in the reaction system, and the reaction solvent.
Solid content concentration (mass%) at the time of imidization reaction = (total mass of tetracarboxylic acid component and diamine component) / (total mass of tetracarboxylic acid component, diamine component, and reaction solvent) × 100

[Polyimide varnish]
The polyimide varnish of the present invention is obtained by dissolving the polyimide resin of the present invention in an organic solvent. That is, the polyimide varnish of the present invention contains the polyimide resin of the present invention and an organic solvent, and the polyimide resin is dissolved in the organic solvent.
The organic solvent may be any one that dissolves the polyimide resin, and is not particularly limited, but it is preferable to use the above-mentioned compounds alone or in combination of two or more as the reaction solvent used for producing the polyimide resin.
The polyimide varnish of the present invention may be a polyimide solution itself in which a polyimide resin obtained by a polymerization method is dissolved in a reaction solvent, or a diluting solvent may be further added to the polyimide solution.

Since the polyimide resin of the present invention has solvent solubility, it can be a varnish having a high concentration stable at room temperature. The polyimide varnish of the present invention preferably contains the polyimide resin of the present invention in an amount of 5 to 40% by mass, more preferably 10 to 30% by mass. The viscosity of the polyimide varnish is preferably 1 to 200 Pa · s, more preferably 1.5 to 100 Pa · s. The viscosity of the polyimide varnish is a value measured at 25 ° C. using an E-type viscometer.
Further, the polyimide varnish of the present invention has an inorganic filler, an adhesion accelerator, a release agent, a flame retardant, an ultraviolet stabilizer, a surfactant, a leveling agent, a defoaming agent, and a fluorescence increase as long as the required properties of the polyimide film are not impaired. Various additives such as a whitening agent, a cross-linking agent, a polymerization initiator, and a photosensitizer may be contained.
The method for producing the polyimide varnish of the present invention is not particularly limited, and a known method can be applied.

[Polyimide film]
The polyimide film of the present invention contains the polyimide resin of the present invention. Therefore, the polyimide film of the present invention is excellent in colorless transparency, optical isotropic property, and chemical resistance (for example, acid resistance and alkali resistance). Suitable physical property values of the polyimide film of the present invention are as described above.
The method for producing the polyimide film of the present invention is not particularly limited, and a known method can be used. For example, the polyimide varnish of the present invention is applied onto a smooth support such as a glass plate, a metal plate, or plastic, or formed into a film, and then an organic solvent such as a reaction solvent or a dilution solvent contained in the varnish is applied. Examples thereof include a method of removing by heating.

Examples of the coating method include known coating methods such as spin coating, slit coating, and blade coating. Above all, the slit coat is preferable from the viewpoint of controlling the intermolecular orientation and improving the chemical resistance and workability.
As a method for removing the organic solvent contained in the varnish by heating, the organic solvent is evaporated at a temperature of 150 ° C. or lower to make it tack-free, and then the temperature is equal to or higher than the boiling point of the organic solvent used (not particularly limited, but preferably). It is preferable to dry at 200 to 500 ° C.). Further, it is preferable to dry in an air atmosphere or a nitrogen atmosphere. The pressure in the dry atmosphere may be reduced pressure, normal pressure, or pressurized pressure.
The method of peeling the polyimide film formed on the support from the support is not particularly limited, but a laser lift-off method or a method of using a sacrificial layer for peeling (a mold release agent is applied to the surface of the support in advance). How to put) can be mentioned.

Further, the polyimide film of the present invention can also be produced by using a polyamic acid varnish in which polyamic acid is dissolved in an organic solvent.
The polyamic acid contained in the polyamic acid varnish is a precursor of the polyimide resin of the present invention and includes a compound giving the above-mentioned structural unit (A-1) and a compound giving the above-mentioned structural unit (A-2). It is a product of a polyaddition reaction between a tetracarboxylic acid component and a diamine component containing the compound giving the above-mentioned structural unit (B-1) and the compound giving the above-mentioned structural unit (B-2). By imidizing (dehydrating and ring-closing) this polyamic acid, the polyimide resin of the present invention, which is the final product, can be obtained.
As the organic solvent contained in the polyamic acid varnish, the organic solvent contained in the polyimide varnish of the present invention can be used.
In the present invention, the polyamic acid varnish may be the polyamic acid solution itself obtained by subjecting the tetracarboxylic acid component and the diamine component to a heavy addition reaction in a reaction solvent, or may be further diluted with respect to the polyamic acid solution. It may be the one to which a solvent is added.

The method for producing the polyimide film using the polyamic acid varnish is not particularly limited, and a known method can be used. For example, a polyamic acid varnish is applied onto a smooth support such as a glass plate, a metal plate, or plastic, or formed into a film, and organic solvents such as a reaction solvent and a diluting solvent contained in the varnish are removed by heating. Then, a polyamic acid film is obtained, and the polyamic acid in the polyamic acid film is imidized by heating to produce a polyimide film.
The heating temperature for drying the polyamic acid varnish to obtain a polyamic acid film is preferably 50 to 120 ° C. The heating temperature for imidizing the polyamic acid by heating is preferably 200 to 400 ° C.
The imidization method is not limited to thermal imidization, and chemical imidization can also be applied.

The thickness of the polyimide film of the present invention can be appropriately selected depending on the intended use and the like, but is preferably in the range of 1 to 250 μm, more preferably 5 to 100 μm, and further preferably 10 to 80 μm. When the thickness is 1 to 250 μm, it can be practically used as a self-supporting film.
The thickness of the polyimide film can be easily controlled by adjusting the solid content concentration and viscosity of the polyimide varnish.

The polyimide film of the present invention is suitably used as a film for various members such as color filters, flexible displays, semiconductor parts, and optical members. The polyimide film of the present invention is particularly preferably used as a substrate for an image display device such as a liquid crystal display or an OLED display.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to these examples.

In Examples and Comparative Examples, each physical property was measured by the method shown below.
(1) Film thickness The film thickness was measured using a micrometer manufactured by Mitutoyo Co., Ltd.
(2) Tensile strength (tensile strength), tensile elastic modulus, tensile elongation (tensile fracture strain)
Tensile strength (tensile strength), tensile elastic modulus and tensile elongation (tensile fracture strain) are based on JIS K7161: 2014 and JIS K7127: 1999, and the tensile tester "Strograph VG-1E" manufactured by Toyo Seiki Co., Ltd. Was measured using. The distance between the chucks was 50 mm, the test piece size was 10 mm × 70 mm, and the test speed was 20 mm / min.
(3) Glass transition temperature (Tg)
Using the thermomechanical analyzer "TMA / SS6100" manufactured by Hitachi High-Tech Science Co., Ltd., residual stress is removed under the conditions of sample size 2 mm x 20 mm, load 0.1 N, and heating rate 10 ° C / min in tensile mode. The temperature was raised to a sufficient temperature to remove residual stress, and then cooled to room temperature. Then, the elongation of the test piece was measured under the same conditions as the treatment for removing the residual stress, and the place where the inflection point of the elongation was observed was determined as the glass transition temperature.
(4) Total light transmittance, yellow index (YI), b ^*
The total light transmittance, YI and b ^* were measured in accordance with JIS K7105: 1981 using a color / turbidity simultaneous measuring device "COH400" manufactured by Nippon Denshoku Industries Co., Ltd.
(5) Thickness phase difference (Rth)
The thickness phase difference (Rth) was measured using an ellipsometer "M-220" manufactured by JASCO Corporation. The value of the thickness phase difference at the measurement wavelength of 590 nm was measured. Rth is expressed by the following formula when the maximum in-plane refractive index of the polyimide film is nx, the minimum is ny, the refractive index in the thickness direction is nz, and the thickness of the film is d. It is a thing.
Rth = [{(nx + ny) / 2} -nz] × d
(6) Polymerization time The polymerization time required for the viscosity to be 12 Pa · s or more when the solid content concentration was 20% by mass was defined as the polymerization time. However, the polymerization time means the time during which the temperature in the reaction system reaches 190 ° C. and is maintained at 190 ° C.
(7) Acid resistance (mixed acid ΔYI and mixed acid Δb ^* )
A mixed acid (HNO ₃ (10% by mass) + H ₃ PO ₄ (70% by mass) + CH ₃ COOH (5% by mass) + H ₂ O (15% by mass)) obtained by warming a polyimide film formed on a glass plate to 40 ° C. The mixture was immersed in a mixed solution for 4 minutes and then washed with water. After washing with water, the water was wiped off, and the mixture was heated on a hot plate at 240 ° C. for 50 minutes to dry. YI and b ^* were measured before and after the test, and their changes (ΔYI and Δb ^* ) were determined. The YI measurement and b ^* measurement here were performed in a state where a polyimide film was formed on a glass plate (a state of a glass plate + a polyimide film).
(8) The polyimide film formed on the alkali-resistant glass plate was immersed in a potassium hydroxide aqueous solution having a concentration of 3% by mass at room temperature for 5 minutes, and then washed with water. After washing with water, it was confirmed that there was no change on the film surface.
The evaluation criteria for alkali resistance are as follows.
A: There was no change on the film surface.
B: The film surface was slightly cracked.
C: The film surface was cracked or the film surface was dissolved.

The tetracarboxylic acid component and diamine component used in Examples and Comparative Examples, other components, and their abbreviations are as follows.
<Tetracarboxylic acid component>
HPMDA: 1,2,4,5-Cyclohexanetetracarboxylic dianhydride (manufactured by Mitsubishi Gas Chemical Company, Inc .; compound represented by formula (a-1))
<Diamine component>
3,3'-DDS: 3,3'-diaminodiphenyl sulfone (manufactured by Seika Co., Ltd .; compound represented by formula (b-1))
BAPS: Bis [4- (4-aminophenoxy) phenyl] sulfone (manufactured by Seika Co., Ltd .; compound represented by formula (b-2))
<Others>
GBL: γ-Butyrolactone (manufactured by Mitsubishi Chemical Corporation)
TEA: Triethylamine (manufactured by Kanto Chemical Co., Inc.)

<Example 1>
3,3'-DDS 14.135g (0) in a 300mL five-necked round-bottom flask with a stainless half-moon agitator, a nitrogen inlet tube, a Dean Stark with a cooling tube, a thermometer, and a glass end cap. .057 mol), BAPS 24.527 g (0.057 mol), and GBL 41.945 g were added and stirred at a system temperature of 70 ° C. and a nitrogen atmosphere at a rotation speed of 200 rpm to obtain a solution.
After adding 25.421 g (0.113 mol) of HPMDA and 10.486 g of GBL in a batch to this solution, 0.573 g of TEA was added as an imidization catalyst, heated with a mantle heater, and reacted over about 20 minutes. The temperature inside the system was raised to 190 ° C. The components to be distilled off were collected, and the temperature inside the reaction system was maintained at 190 ° C. and reflux was carried out for about 5 hours while adjusting the rotation speed according to the increase in viscosity.
Then, 187.569 g of GBL was added so as to have a solid content concentration of 20% by mass, the temperature inside the reaction system was cooled to 100 ° C., and the mixture was further stirred for about 1 hour to homogenize to obtain a polyimide varnish. The viscosity of the varnish solution was 12 Pa · s at 25 ° C.
Subsequently, the obtained polyimide varnish was applied onto a glass plate by spin coating, held on a hot plate at 80 ° C. for 20 minutes, and then heated in a hot air dryer at 260 ° C. for 30 minutes in an air atmosphere to evaporate the solvent. And obtained a film. The results are shown in Table 1.

<Example 2>
3,3'-DDS 17.571g (0) in a 300mL five-necked round-bottom flask equipped with a stainless half-moon agitator, a nitrogen inlet tube, a Dean Stark with a cooling tube, a thermometer, and a glass end cap. .071 mol), BAPS 20.326 g (0.047 mol), and GBL 42.041 g were added and stirred at a system temperature of 70 ° C. and a nitrogen atmosphere at a rotation speed of 200 rpm to obtain a solution.
After adding 26.333 g (0.117 mol) of HPMDA and 10.510 g of GBL in a batch to this solution, 0.594 g of TEA was added as an imidization catalyst, and the mixture was heated with a mantle heater over about 20 minutes. The temperature inside the reaction system was raised to 190 ° C. The components to be distilled off were collected, and the temperature inside the reaction system was maintained at 190 ° C. and refluxed for about 4.7 hours while adjusting the rotation speed according to the increase in viscosity.
Then, 187.449 g of GBL was added so as to have a solid content concentration of 20% by mass, the temperature in the reaction system was cooled to 100 ° C., and the mixture was further stirred for about 1 hour to homogenize to obtain a polyimide varnish. The viscosity of the varnish solution was 12 Pa · s at 25 ° C.
Subsequently, the obtained polyimide varnish was applied onto a glass plate by spin coating, held on a hot plate at 80 ° C. for 20 minutes, and then heated in a hot air dryer at 260 ° C. for 30 minutes in an air atmosphere to evaporate the solvent. And obtained a film. The results are shown in Table 1.

<Comparative example 1>
3,3'-DDS 5.122 g (0) in a 300 mL five-necked round-bottom flask equipped with a stainless half-moon agitator, a nitrogen inlet tube, a Dean Stark with a cooling tube, a thermometer, and a glass end cap. .021 mol), BAPS 35.549 g (0.082 mol), and GBL 41.694 g were added and stirred at a system temperature of 70 ° C. and a nitrogen atmosphere at a rotation speed of 200 rpm to obtain a solution.
After adding 23.028 g (0.103 mol) of HPE and 10.388 g of GBL in a batch to this solution, 0.519 g of TEA was added as an imidization catalyst, heated with a mantle heater, and reacted over about 20 minutes. The temperature in the system was maintained at 190 ° C., and the mixture was refluxed for about 7 hours. The viscosity of the varnish solution was 12 Pa · s at 25 ° C.
Then, 187.883 g of GBL was added so as to have a solid content concentration of 20% by mass, the temperature inside the reaction system was cooled to 100 ° C., and the mixture was further stirred for about 1 hour to homogenize to obtain a polyimide varnish.
Subsequently, the obtained polyimide varnish was applied onto a glass plate by spin coating, held on a hot plate at 80 ° C. for 20 minutes, and then heated in a hot air dryer at 260 ° C. for 30 minutes in an air atmosphere to evaporate the solvent. And obtained a film. The results are shown in Table 1.

<Comparative example 2>
3,3'-DDS 25.239 g (0) in a 300 mL five-necked round-bottom flask equipped with a stainless half-moon agitator, a nitrogen inlet tube, a Dean Stark with a cooling tube, a thermometer, and a glass end cap. .101 mol), BAPS 10.949 g (0.025 mol), and GBL 42.255 g were added and stirred at a system temperature of 70 ° C. and a nitrogen atmosphere at a rotation speed of 200 rpm to obtain a solution.
After adding 28.369 g (0.126 mol) of HPMDA and 10.564 g of GBL in a batch to this solution, 0.640 g of TEA was added as an imidization catalyst, heated with a mantle heater, and reacted over about 20 minutes. The temperature inside the system was raised to 190 ° C. The components to be distilled off were collected, and the temperature inside the reaction system was maintained at 190 ° C. and reflux was carried out for about 7.5 hours while adjusting the rotation speed according to the increase in viscosity.
Then, 187.181 g of GBL was added so as to have a solid content concentration of 20% by mass, the temperature inside the reaction system was cooled to 100 ° C., and the mixture was further stirred for about 1 hour to homogenize to obtain a polyimide varnish. The viscosity of the varnish solution was 12 Pa · s at 25 ° C.
Subsequently, the obtained polyimide varnish was applied onto a glass plate by spin coating, held on a hot plate at 80 ° C. for 20 minutes, and then heated in a hot air dryer at 260 ° C. for 30 minutes in an air atmosphere to evaporate the solvent. And obtained a film. The results are shown in Table 1.

As shown in Table 1, the polyimide films of Examples 1 and 2 used HPMDA as the tetracarboxylic acid component, and 50 to 60 mol% of 3,3'-DDS and 50 to 40 mol% of BAPS as the diamine component. Manufactured in combination. As a result, it exhibited colorless transparency, optical isotropic property, acid resistance, and alkali resistance, and was excellent in toughness. Furthermore, the polymerization time was shorter than that of the comparative example.
On the other hand, the polyimide film of Comparative Example 1 was produced by using HPMDA as a tetracarboxylic acid component and using 20 mol% of 3,3'-DDS and 80 mol% of BAPS in combination as a diamine component. As a result, the thickness retardation (Rth) was high and the optical isotropic property was inferior. In addition, the polymerization time was long.
The polyimide film of Comparative Example 2 was produced by using HPMDA as a tetracarboxylic acid component and using 80 mol% of 3,3'-DDS and 20 mol% of BAPS in combination as a diamine component. As a result, although the thickness retardation (Rth) was low and the optical characteristics were excellent, the tensile elongation and tensile strength were low and inferior. In addition, the polymerization time was long.
Therefore, a polyimide film produced by using HPMDA as a tetracarboxylic acid component and 3,3'-DDS and BAPS as a diamine component in a specific ratio has colorless transparency, optical isotropic property, and chemical resistance ( For example, it can be suitably used as a plastic substrate for a liquid crystal display, a touch panel, etc. as a film having excellent acid resistance and alkali resistance) and toughness. Further, the polymerization time is short, the energy during production can be reduced, and the production cost is excellent.

Claims

A polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine.
The structural unit A includes a structural unit (A-1) derived from a compound represented by the following formula (a-1), and a structural unit (A) derived from a compound represented by the following formula (a-2). -2) is not included,
A structural unit (B-1) in which the structural unit B is derived from a compound represented by the following formula (b-1) and a structural unit (B-2) derived from a compound represented by the following formula (b-2). Including and
A polyimide resin in which the ratio of the structural unit (B-1) in the structural unit B is 30 to 70 mol%, and the ratio of the structural unit (B-2) in the structural unit B is 70 to 30 mol%.
A polyimide varnish in which the polyimide resin according to claim 1 is dissolved in an organic solvent.
A polyimide film containing the polyimide resin according to claim 1.